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RE: (meteorobs) Thinking about low radiant height




> when the radiant height is low, also meteors simply are farther 
> away and so fainter

I don't think this is true. Once the radiant is above the horizon, meteors can appear anywhere in the sky. They are not limited to the radiant, so they can also appear directly overhead. Because they enter the atmosphere nearly parallel to the surface of the observer they will generaly be very long at that time, the so called earthgrazers.

>   fractional sky, atmospheric extinction, and also simply greater distance

The fractional sky is indeed related to radiant height (I assume you refer to the fact that when the radiant is low for an observer, there is only a very small hole through which a meteor can enter the atmosphere above the observer)

Extinction and distance are related to the apparent position of the actual meteor, I recall an article and message by James Richardson in which he gives an approximation for the extintion in magnitudes:

 -5    * log( sec( ZA ) )    for the distance
 -2.5 * log( sec( ZA ) )    for atmospherice absorption

ZA is the angle between Zenith and the !Meteor! In the message James talks about the radiant height, but he corrects this in a follow up.

Daniel

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